Calibration of Gaussmeters at Axial DC Magnetic Field Direction up to 1 Tesla at SCL

Calibration of Gaussmeters at Axial DC Magnetic Field Direction up to 1 Tesla at SCL

Speaker: Chung Yin, PoonStandards and Calibration Laboratory (SCL)The Government of the Hong Kong Special Administrative Region#Standards and Calibration Laboratory, SCL1Measurement on DC magnetic flux densityMeasurement instrumentsGaussmeter with Hall Effect transverse / axial test probeNuclear Magnetic Resonance (NMR) gaussmeter

Sources of magnetic flux density

#Standards and Calibration Laboratory, SCL2Sources of Magnetic Flux Density

Helmholtz CoilsElectromagnet#Standards and Calibration Laboratory, SCL3Calibration on Axial Direction

Test probe of the DUT(located at the z-axis of the Helmholtz coil)

Test probe of the Reference Meter (located at the x-axis of the Helmholtz coil)

B field direction

#Standards and Calibration Laboratory, SCL4Calibration on Axial Direction

B field direction

for axial measurement x#Standards and Calibration Laboratory, SCL5Calibration Needs on Axial FieldToy Safety StandardASTM F963-08 Section 8.24 Magnet Test Method Measurement parameter : magnetic flux density ( gauss / Tesla ) Equipmentdc field gauss meter with a resolution of 5 gauss (G) and an axial type probe. An active area diameter of 0.76 +/- 0.13 mm A distance between the active area and probe tip of 0.38 +/- 0.13 mm. Medical electrical equipment Safety (e.g. IEC 60601-2-33)#Standards and Calibration Laboratory, SCL6Automatic calibration system on DC magnetic flux density for working-grade gaussmeter in SCL#Standards and Calibration Laboratory, SCL7An automatic calibration system in SCLThe major components of the system containA modified electromagnetThe electromagnets power supplyA water cooling system for the modified electromagnetA reference gaussmeterA software controlled program#Standards and Calibration Laboratory, SCL8A modified electromagnet system in SCL

Small opening at the yoke with size and shape suitable for positioning a common test probe in an axial magnetic field#Standards and Calibration Laboratory, SCL9Photos of the electromagnet

Filler rodOpening at the yoke test probe of the tested unittest probe of reference meter#Standards and Calibration Laboratory, SCL10Characterization of the Modified ElectromagnetField Plot with the opening at the RHS yoke

pole diameter = 150 mm ; pole gap = 20 mm; z-axis along the pole axistoward the RHS yoke with openingAt the center of the yoke#Standards and Calibration Laboratory, SCL11Characterization of the Modified ElectromagnetField Plot with filler rod inserted in the RHS yoke

pole diameter = 150 mm ; pole gap = 20 mm; z-axis along the pole axis#Standards and Calibration Laboratory, SCL12Setup of Calibration

The measurement will be taken at the location adjacent to the LHS yoke ( i.e. as far away from the opening (i.e. RHS yoke ) )#Standards and Calibration Laboratory, SCL13Field Uniformity

On the surface of the LHS yokeZ = 4 mm ; field uniformity ~ 500 x 10-6Z = 7 mm ; field uniformity ~ 200 x 10-6#Standards and Calibration Laboratory, SCL14

Automation of the calibrationThe software tool using Visual Basic for the automatic calibration of working-grade gaussmter which have either IEEE 488, RS232 or USB interface. number of measurements; magnetic field levels for test; polarity of the test field ;settings of the reference meter ;settings of the UUTTest field levels are sorted in ascending order by the programInitial value = (Requested test level )/(electromagnet coefficient)#Standards and Calibration Laboratory, SCL15Measurement UncertaintyUncertainty contributions due toField non-uniformityCalibration setupPerformance of the test unitPerformance of the reference meterEnvironmental effects

The best calibration and measurement capability of the working grade gaussmeter is 0.1 % from 50 mT to 1.0 T for axial direction (k=2, 95% CL)#Standards and Calibration Laboratory, SCL16Thank you#Standards and Calibration Laboratory, SCL